Synthetic vision systems (SVS) can provide pilots and crews with enhanced situational awareness in low visibility environments such as those resulting from darkness or adverse weather conditions. For example, during approach and landing segments, it is critical for the pilot to clearly perceive the runway and any obstacles that might interfere with a stable approach. However, neither the runway nor the surrounding environment may be clearly visible. In addition, synthetic vision systems may enhance situational awareness during other flight segments; for example, providing information about glide slope or recovery from unusual attitude under extreme conditions.
Synthetic vision systems generally incorporate an enhanced vision system (EVS) including multiple sensors (such as optical or infrared cameras) configured to extract visual information in a low-visibility environment. However, EVS visual sensors may not always provide the pilot with all available visual intelligence. For example, EVS sensors may not be able to detect LED runway lighting. Different sensors may provide higher, or lower, visibility depending on environmental conditions (e.g., smoke, fog, darkness). Additionally, position errors associated with GPS receivers may result in imprecise results from the SVS. In other words, under low-visibility or zero-visibility conditions where the pilot is dependent on the SVS, a GPS error of several feet may result in the aircraft being portrayed by the SVS as occupying a different location than it actually occupies. Imprecise SVS results may lead the pilot to attempt approach or landing in an undesirable location, or forgo a landing in a desirable location. More critically, a combination of detailed environmental information and imprecise position data may cause the aircraft to collide with an avoidable obstacle. In underserved or GPS-denied areas, the pilot may not be able to rely on GPS information at all. It may therefore be desirable to enhance the accuracy of both the visual intelligence and position information provided to the SVS.